This application is the U.S. national phase of international application PCT/GB01/01882 filed Apr. 30, 2001, which designated the U.S.
The present invention relates to saw blades and in particular, to a method of making a saw blade blank and a saw blade therefrom.
The invention provides a method of making a saw blade blank, in which at least one aperture is formed in a strip of relatively soft material and an insert of relatively hard material is fixed in the aperture, the insert causing material of the blank to be displaced as the insert is introduced, and material being removable from the edge of the blank to form a saw blade with a tooth, leaving at least part of the insert exposed to form a cutting portion of the tooth.
The aperture may be formed by the insertion of the insert, or may be formed prior to insertion of the insert.
Preferably the entire circumference of the aperture is spaced from the edge of the blank.
Preferably a plurality of apertures are formed for respective inserts. The apertures may be regularly spaced along the blank and may be equally spaced from the edge of the blank. Alternatively, the apertures may be spaced by different distances from the edge of the blank, to allow composite teeth to be formed with cutting portions at different separations from the body of the blank. The pitch of the apertures along the blank may vary along the blank.
The or each aperture may be circular. The insert may be non-circular. The insert may comprise a main body from which at least one projection extends, the projection serving to displace material of the strip when the insert is introduced, and thereafter to remain embedded within the material of the strip. Preferably a plurality of projections as aforesaid are provided on the insert. The projections may each have a convex extremity and be separated from neighbouring projections by a concave portion of the outline of the insert.
A portion of the outline of the insert may have the shape of the required cutting portion, prior to insertion. The aperture may open to the edge of the blank, the insert being positioned in the aperture to leave the shaped portion exposed.
Preferably at least one dimension of the insert is less than the corresponding dimension of the aperture in the plane of the blank, to cause a gap to be left between the blank and the insert when positioned in the aperture, the gap serving to receive additional material for fixing the insert in the aperture. The fixing material may be weld or brazing flux.
Preferably the inserts are tungsten carbide, and may be sintered. The blade may be steel.
The invention also provides a saw blade blank manufactured according to the method set out above.
The invention also provides a saw blade blank comprising a strip of relatively soft material, an aperture formed in the strip, an insert of relatively hard material fixed in the aperture and sufficiently large to cause material of the blank to be displaced by the introduction of the insert, whereby material may be removed from the edge of the blank to form a tooth, at least part of the insert being exposed in the finished blade to form a cutting portion of the tooth.
The blade blank may have any of the features set out above.
The invention also provides a method of making a saw blade from a saw blade blank manufactured according to the method as set out above, comprising removing material from the edge of the blank to form a tooth, at least part of the insert being exposed in the finished blade to form a cutting portion of the tooth.
The invention also provides a saw blade manufactured according to the method set out above.
The invention also provides a saw blade comprising a strip of relatively soft material, an insert of relatively hard material fixed in an aperture in the strip and sufficiently large to cause material of the blank to be displaced by the introduction of the insert, and the strip having material removed from its edge to form a tooth, at least part of the insert being exposed in the blade to form a cutting portion of the tooth.
The blade may have any of the features set out above.